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Differential signal of change among multiple components of West African rainfall

Abstract

Rainfall components likely differ in the magnitude and direction of their long-term changes for any given location, and some rainfall components may carry a greater regional signal of change than rainfall totals. This study evaluates the magnitude of change of multiple rainfall components relative to other components, and the greatest regions of change across all rainfall components in West Africa. Hourly rainfall data from the ERA5 reanalysis dataset was used to derive twelve rainfall components, which were evaluated for long-term means, interannual variability, and long-term changes. For rainfall totals and rainfall intensity, the central Sahel is witnessing increasing trends while the western Sahel is experiencing significant decreasing trends. In general, decreasing trends predominate in the study domain, especially in the northwestern Congo Basin, where annual rainfall is decreasing by 120 mm per decade. Importantly, rainfall frequency accounts for 49% of all significant grid-point trends for the whole domain. In contrast, rainfall totals account for 26% of all combined significant trends across the domain, while rainfall intensity (12.6%), rainy season length (9.5%), and seasonality (3.3%) account for the remaining signals of change. Most of the changes among the rainfall components are in the tropical wet and dry regions (59% of all significant trends); the Saharan and equatorial regions account for the least changes. This study finds evidence that rainfall frequency is changing more across the regions compared to rainfall totals and should be explored as rainfall inputs in climate models to potentially improve regional predictions of future rainfall.

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Data Availability

Precipitation data used in this study is publicly available at their respective website and data repository as cited in this study.

Code availability

MATLAB software was used entirely. Codes are available from the corresponding author on reasonable request.

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Acknowledgements

This research was improved considerably by the suggestions of Dr. Scott Sheridan and Dr. Thomas Schmidlin in the Department of Geography at Kent State University. The authors are also grateful to Eric Tyler Smith and Ryan Adams for their help with MATLAB coding.

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All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Omon Obarein] and [Cameron Lee]. The first draft of the manuscript was written by [Omon Obarein] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

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Correspondence to Omon A. Obarein.

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Obarein, O.A., Lee, C.C. Differential signal of change among multiple components of West African rainfall. Theor Appl Climatol 149, 379–399 (2022). https://doi.org/10.1007/s00704-022-04052-1

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  • DOI: https://doi.org/10.1007/s00704-022-04052-1